SIP-based Location Aware Services

In this paper, we investigate the prospects of using Session Initiation Protocol (SIP) in context—aware services. We focus on the location-based paradigm in which the users' location is the contextual parameter used for service adaptation and delivery. We present the general steps required to achieve this and elaborate on an architecture that uses a SIP-enabled Value Added Service Provider as the main component responsible for the provision and delivery of the service. The pilot implementation carried out exploits the general ability of SIP to embed user specific information in the message body of the exchanged messages. Session Initiation Protocol (SIP) [RFC2543] is a simple, Internet–based session control protocol that was introduced mainly in order to establish and terminate calls over the Internet (VoIP). However, its simplicity and versatility has made it a prime candidate in the development of new services (e.g. Instant Messaging [RFC2778]), as well as a key technology enabler for supporting new signalling capabilities within next generation services. Many competitive Telecom Operators are already using SIP for initial service provision and SIP based solutions are emerging rapidly all over the globe. On the other hand, context-aware computing is a mobile computing paradigm in which applications can discover and take full advantage of contextual information (such as user geographical location, time of day, type of terminal/device, user activity, etc.). The applications are then delivered to the user customized to its current context. In supporting such types of transactions, SIP appears as an ideal solution. It can be used initially for the context discovery (by properly using certain header fields or information carried in the message body of a SIP request) and later on for the connection establishment and termination of the service. In the present article, we explore the capabilities of using SIP in support of context– aware applications. We focus on an architecture where SIP is used in the control plane to signal the current context of the user to the information provider, and the delivered content specific information is based on the user's current location. The rest of the paper is organised as follows. In Section 2 we survey related work. In Section 3 we describe the architecture of the proposed system. Starting with a high level description of the system, we continue with a more detailed analysis of each individual component and conclude by presenting the complete interaction and message exchange between them. We present the …